1. Field of the Invention
The present invention relates to a new pressure swing adsorption process, and to apparatus for separating at least one gas component from a gas mixture, such a separation of nitrogen and oxygen from air, for example. More particularly, the invention relates to an improved desorption procedure, and to an apparatus for practicing it.
Still further, the invention relates to an improved pressure swing desorption procedure and to an apparatus suitable for carrying it into effect for recovering or collecting at least one selectively adsorbable gas component, at a substantially constant flow rate, from a gas mixture.
2. Description of the Prior Art
Pressure swing adsorption processes for separating gas mixtures having selectively adsorbable components are well known (for example, reference is made to Japanese Pat. publication 25069/1963). These processes consist, as fundamental steps, of (1) an adsorption step conducted at a relatively high pressure and (2) a desorption step conducted with pressure reduction. In industrial processes, however, it is the general practice that at least one additional step is combined with the fundamental steps (1) and (2) for recovering a selectively adsorbable component economically. The additional operation step may also be used to recover a less selectively adsorbable component from the gas mixture, in satisfactory yield and in a pure state.
Various improvement attempts have been made relating to these and other additional steps. When it is desired to recover a selectively adsorbable gas component in high purity, for example, purging with a pure gas of the selectively adsorbable component may be practiced prior to the desorption step (reference is made, for example, to U.S. Pat. No. 3,797,201).
It is also important to recover a gas which is enriched with at least one selectively adsorbable gas component at a constant flow rate. This is particularly true when the gas is utilized for other industrial purposes.